A typical internal combustion engine includes a main cooling circuit configured to allow coolant, such as water, to flow through a radiator. A bypass conduit opens during a start phase of the engine and allows the coolant to circulate through the bypass conduit. In general, a thermostatic valve system controls the flow of coolant. At least one valve is driven by a thermally expansive member and fit with a bypass valve. The valves are connected to each other such that, at a predefined lower temperature, the thermostatic valve is closed and the bypass valve is open. As the temperature increases, the thermostatic valve opens, and the bypass valve gradually closes. WO2010/061343, entitled “A Cooling System For A Combustion Engine,” which is hereby incorporated by reference in its entirety, provides further details of a cooling system.
A typical ball valve thermostat assembly includes a fail-safe return member and utilizes a control unit that is configured to drive the valve in both open and closed directions. However, the valve is generally only electrically driven in the closed direction. During a cold start, the valve is driven to the closed position so that the engine may be quickly heated. When temperatures are extremely cold, the motion of the fail-safe return member is generally slower than at normal operating temperatures. If the engine is revved when the outside temperature is extremely cold, and the valve is in the closed position, high pressures may develop within the cooling system. The resulting high pressures may damage the cooling system and the engine.
FIG. 1 illustrates a graph of typical valve operation within a coolant regulator. As shown, angular valve positions of 0 degrees and 93 degrees provide hard physical stops within the coolant regulator. Angular valve positions of 5 degrees and 88 degrees provide soft stops. To close the valve, the valve is electrically actuated to a rotated position of 88 degrees. To re-open the valve, the electrical signal is stopped and the return spring opens the valve. The valve can be stopped at any angle by applying sufficient electrical energy to stop the valve without moving it back toward the open (or closed) position.
However, as pressure increases within the coolant regulator, the closed position of the valve generally prevents fluid from passing therethrough. As such, fluid pressure within the coolant regulator may build and damage the coolant regulator and/or the engine. Accordingly, a need exists for a system and method of relieving pressure within a coolant regulator.